In connection with obtaining materialographic samples, pieces of a material, e.g. a metal, are cut by abrasive cut off wheels in, for example, materialographic cutting machines, such as metallographic cutting machines.
After a sample has been cut by a cut off wheel, the sample needs to be prepared for examination by one or more of grinding, lapping and polishing a surface of the sample often in a stepwise finer manner.
Grinding may be defined as the rapid and often initial removal of material from a specimen either to reduce the specimen to a suitable size or to remove large irregularities from the surface.
Lapping may be defined as the removal of material to produce a smooth, flat, unpolished surface. Lapping processes are used to produce dimensionally accurate specimens to high tolerances.
Polishing may be defined as is the removal of material to produce a scratch-free, specular surface. Polishing is typically done at very low speeds using either polishing cloths, abrasive films, or specially designed lapping plates.
Prior to preparation for examination, the samples are placed in, or molded in, a base for easy handling. The base may constitute a sample holder.
For the purpose of obtaining and examining e.g. metallographic samples, which typically are cylindrical, test objects are, as mentioned above, prepared by one or more of grinding, lapping and subsequently polishing. In between each step, the metallographic sample needs to be rinsed to remove coarse-grained debris and abrasives before the next and finer step to avoid contaminating the following preparation procedure.
The normal procedure for rinsing such metallographic samples typically involves manually transferring the metallographic sample to a sink, washing the metallographic sample in a special soap, then in alcohol/methylated spirit, and manually drying the metallographic sample, either using a cloth, blow drying, or both. This procedure is described in e.g. the ASTM standard; Geels, Kay: “Metallographic and Materialographic Specimen Preparation, Light Microscopy, Image Analysis and Hardness Testing”; Lancaster, Pa., US, June 2007, section 5.1.2 (pages 82-83).
It is a problem of the prior art that these actions are hard to perform without getting smeared, and there is a risk of contaminating the sample. Further, it is difficult or not possible to obtain a constant quality of rinsing, whereby, replicability in the sampling procedure is diminished. Yet further, the handling of special soap or alcohol is at risk of inducing health and environmental problems. Yet further, it is hard to control the use of water, soap and alcohol in the manual process, often causing excess use, which increases the cost and waste product, the latter, especially, being a potential environmental problem.
Also known in the art is a machine where a number of metallographic samples are placed in a holder and where the samples are stepwise ground/polished. In between each step, an arm transports the holder with the metallographic sample from the grinding site to a chamber filled with soap water, submerging the holder into the soap solution, and subjecting the holder with the metallographic samples to ultrasonic waves. Subsequently, the arm extracts and transports the metallographic sample from the soap solution chamber and into a separate chamber, wherein clean water under pressure is sprayed on the soap-water soaked holder with the samples to rinse of the soap and any debris on the holder and metallographic samples. Finally, in the same chamber, the holder and the metallographic samples are dried by pressurized air. Such a machine is provided by the applicant under the name Hexamatic and MAPS.
It is a problem, with the prior art device that it uses larger quantities of detergents/chemicals, and relatively large quantities of energy for drying.
Further, despite being a fully automated device, the process is slow if the rinsing quality is to be kept sufficiently high. Under section 5.1.2 the ASTM standard; Geels, Kay: “Metallographic and Materialographic Specimen Preparation, Light Microscopy, Image Analysis and Hardness Testing”; Lancaster, Pa., US, June 2007, also mentions the use of ultrasound to clean specimens, where the specimens are placed in a tank filled with water with a detergent, alcohol or organic solvent. In cases where the samples are particularly dirty, Geels suggest to use weak acids or basic solutions.
U.S. Pat. No. 5,985,811 A discloses a method of spray cleaning semiconductors by rotating the material to be cleaned in a cleaning vessel while applying ultrasound to a flow of cleaning liquid being fed to the spraying nozzle. Ultrasound is applied to the cleaning liquid with the purpose of generating free radicals in order to facilitate cleaning the semiconductors.
U.S. Pat. No. 7,317,964 B1 discloses a method of 3D high precision reconstruction of microstructure specimens.
CN 103447937 A discloses an automatic grinding and polishing machine. According to the reference, after polishing of the samples is completed, the samples are moved into an ultrasonic washing box to carry out washing of the samples.
U.S. Pat. No. 6,247,198 B discloses an apparatus for cleaning a wafer. The wafer is cleaned by brushes and placed in a cleaning liquid. Furthermore, ultrasonic vibrations are applied to the cleaning liquid by an ultrasonic generator.
US 2004/163682 A discloses a method for cleaning a semiconductor. The method initiates with generating acoustic energy oriented in a substantially perpendicular direction to a surface of a semiconductor substrate. Then, acoustic energy oriented in a substantially parallel direction to the surface of the semiconductor substrate is generated.